1. Field of the Invention
The present invention relates to a sheet feeder device and an image forming apparatus.
2. Related Art
An image forming apparatus, such as a copier, printer and facsimile machine, is generally provided with: an image carrier (photoreceptor drum); a developer which converts an electrostatic latent image formed on the image carrier into a toner image; a toner container (also called “toner cartridge” or the like) which stores the toner; a transfer unit which transfers the toner image formed on the image carrier onto a sheet of paper or the like; a fixing unit which fixes the toner image transferred to the paper; and a sheet feeder device having a sheet feeder which conveys a sheet of paper to the transfer unit, the fixing unit, and the like, and a sheet feed cassette which stores a plurality of stacked sheets of paper, which is to be sent to the transfer unit, and a cassette housing which houses the sheet feed cassette.
When the sheet feed cassette of the sheet feeder device, which stores stacked sheets of paper, is housed in the cassette housing, the sheet feeder device causes a pickup roller to rotate to feed a topmost sheet of paper in a feed direction to the fixing unit, while the pickup roller provided in the cassette housing presses from above the topmost sheet of paper located at the top of the plurality of stacked sheets of paper.
In order to store a plurality of sets of stacked sheets of paper having various sizes set by set, the paper feed cassette is provided with an end adjustment guide configured to align ends of the plurality of stacked sheets of paper in the feed direction and a pair of width adjustment guides configured to align the plurality of stacked sheets of paper in a width direction. Size of a sheet of paper included in the plurality of stacked sheets of paper includes one of B5 size, B4 size, and A3 size (based on Japan Industrial Standard (JIS)), for example. In addition, there may be different directions with respect to the arrangement of the plurality of stacked sheets of paper: the longer direction or shorter direction coincides with the feed direction.
For example, a sheet feeder device is proposed which usually feeds a topmost sheet of paper in the feed direction with one pickup roller regardless of the size of the stacked sheets of paper stored in the paper feed cassette. In this example, the pickup roller is configured to apply a larger pressing force to press the topmost sheet of paper so that a sheet of paper of the largest size storable in the paper feed cassette is fed reliably.